The technique of forming a metal layer on a polymer substrate in order to transmit electro-magnetic signals is widely used in fields like automobiles, computers, communications, etc. Selectively forming the metal layer on the surface of the polymer substrate is a key step in this technique.
One method for selectively metalizing a surface of a polymer substrate includes the following steps. First, a catalyst or accelerator for chemical plating is adhered on the surface of the polymer substrate which is to be plated. Then, metal ions in a metal solution for chemical plating are reduced to pure metal via an oxidation-reduction reaction, and the pure metal are deposited on the surface of the polymer substrate, thus forming a metal layer on the polymer substrate.
For example, Chinese Patent Application No. CN102752962A discloses a substrate provided with a metal layer and a manufacturing method of the substrate provided with the metal layer. The manufacturing method includes the steps of forming a hydrophilic region or a hydrophobic region on a surface of the substrate by performing surface treatment with plasma, and attaching a catalyst layer or an exchange layer or an isolating layer formed by organic or inorganic substances on the hydrophilic or hydrophobic surface of the substrate by using a surface treatment solution; then using a metal solution to form the metal layer on the surface of the catalyst layer or the exchange layer due to catalytic reaction or exchange reaction. The isolating layer can protect other regions from metal deposition, and the metal layer attached to the substrate can be patterned, so as to be used as a circuit contact or line. The manufacturing method, however, has disadvantages of complicated processing steps and weak adhesion between the metal layer and the polymer substrate.
Another method for selectively metalizing a surface of a polymer substrate includes the following steps. First, a polymer material is mixed with a catalyst or an accelerator for chemical plating or a precursor thereof, and molded to form a polymer substrate with the catalyst or accelerator or precursor thereof dispersed therein. Before the step of chemical plating, a surface of the polymer substrate is irradiated with an energy beam such as a laser, such that a part of polymer material in the irradiated surface is gasified and the catalyst or accelerator or precursor thereof is exposed. Then, chemical plating is performed on the irradiated surface to form a metal layer on the surface of the polymer substrate. In case the precursor is used, the precursor can be activated by the energy beam to form the catalyst or accelerator.
For example, U.S. Patent Application Publication No. 2004/0241422A1 discloses a method for preparing a polymer article, which includes steps of: adding an inorganic compound having a spinel structure and containing Cu, Ni, Co, Cr, Fe, etc. to a polymer matrix, and activating the inorganic compound with an ultraviolet laser (with wavelengths of 248 nm, 308 nm, 355 nm, 532 nm) and an infrared laser (with wavelengths of 1064 nm and 10600 nm). Specifically, the patent mentions that the oxides having spinel structures should be reduced into metal under the effect of the laser. Then, the metal may act as a crystal core, onto which metal may be deposited during a chemical plating process so as to form a metal layer. However, the energy of the laser has to be high enough to reduce the oxides having the spinel structure into pure metal. Therefore, the method has on the one hand serious damage on the polymer matrix, and on the other hand the adhesion between the metal layer and the substrate is weak.
As another example, Chinese Patent Application No. CN103313523A discloses a manufacturing method for an electronic circuit. The manufacturing method includes the following steps of: preparing a circuit carrier, wherein the circuit carrier is made of a high-molecular compound and a water repellent agent is added in the high-molecular compound; carrying out selective electromagnetic irradiation on the surface of the circuit carrier to form a hydrophilic area; and carrying out electroplating or chemical plating on the circuit carrier to enable a metal material to be attached in the hydrophilic area and form the electronic circuit.
As described above, methods for selectively metalizing a surface of a polymer substrate still need to be modified. In terms of these methods, it is generally believed that the oxidation-reduction reaction mainly takes place on the hydrophilic surface, while it is difficult to form a complete metal layer on the hydrophobic surface.